Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$88.76	4.308%	$92.5838	$92.58	$92.60	$92.60
Purchase #2	$115.70	8.545%	$125.5866	$125.59	$125.60	$125.60
Purchase #3	$40.47	12.837%	$45.6651	$45.67	$45.65	$45.70
Purchase #4	$98.64	5.864%	$104.4242	$104.42	$104.40	$104.40
Purchase #5	$139.55	6.347%	$148.4072	$148.41	$148.40	$148.40
Purchase #6	$241.98	6.762%	$258.3427	$258.34	$258.35	$258.30
Purchase #7	$227.31	3.176%	$234.5294	$234.53	$234.55	$234.50
7 purchase totals =	$952.41		$1,009.5390	$1,009.54	$1,009.55	$1,009.50